Pore size distributions derived from adsorption isotherms, immersion calorimetry, and isosteric heats: A comparative study

S. Hadi Madani, Cheng Hu, Ana Silvestre-Albero, Mark J. Biggs, Francisco Rodríguez-Reinoso, Phillip Pendleton

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27 Citations (Scopus)

Abstract

We compare the pore size distribution of a well-characterized activated carbon derived from model-dependent, adsorption integral equation (AIE) methods with those from model-independent, immersion calorimetry and isosteric heat analyses. The AIE approach applied to nitrogen gave a mean pore width of 0.57 nm; the CO2 distribution exhibited wider dispersion. Spherical model application to CO2 and diffusion limitations for nitrogen and argon were proposed as primary reasons for inconsistency. Immersion enthalpy revealed a sharp decrease in available area equivalent to a cut-off due to molecular exclusion when the accessible surface was assessed against probe kinetic diameter. Mean pore width was identified as 0.58 ± 0.02 nm, endorsing the underlying assumptions for the nitrogen-based AIE approach. A comparison of the zero-coverage isosteric heat of adsorption for various non-polar adsorptives by the porous test sample was compared with the same adsorptives in contact with a non-porous reference adsorbent, leading to an energy ratio or adsorption enhancement factor. A linear relationship between the energy ratio and probe kinetic diameter indicated a primary pore size at 0.59 nm. The advantage of this enthalpy, model-independent methods over AIE were due to no assumptions regarding probe molecular shape, and no assumptions for pore shape and/or connectivity.

Original languageEnglish
Pages (from-to)1106-1113
Number of pages8
JournalCarbon
Volume96
DOIs
Publication statusPublished - Jan 2016

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

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    Madani, S. H., Hu, C., Silvestre-Albero, A., Biggs, M. J., Rodríguez-Reinoso, F., & Pendleton, P. (2016). Pore size distributions derived from adsorption isotherms, immersion calorimetry, and isosteric heats: A comparative study. Carbon, 96, 1106-1113. https://doi.org/10.1016/j.carbon.2015.10.072